Ponente: Sebastián Carrazco Gaxiola (Georgia State University)
Título: "RKSTAR’s Southern K dwarfs within 40 pc: Kinematics, Lithium, and Chromospheric Activity"
Resumen: More than twice as common as G dwarfs like the Sun, K dwarfs account for 11% of all stars in the solar neighborhood. Their abundance and slow evolutionary timescales make them valuable for stellar‑population studies, as well as promising hosts for exoplanets. Yet they have not received the same level of characterization available for both G dwarfs and cooler M dwarfs. Here we present the results of a complete, volume-limited, south hemisphere spectroscopic survey of nearly 1600 K dwarfs within 40 pc, as part of the RKSTAR (RECONS K STAR) Project. We use CHIRON high-resolution spectrograph (R=80,000) spectrograph, located at the SMARTS-GSU 1.5m at CTIO, to observe 1612 K dwarfs primaries within 40 pc with DEC = +30° to -90°. Using Gaia’s astrometry and accurate radial velocities, we find that about 11% of stars are active and/or young by 1) measuring chromospheric activity and youth indicators, including Hα, Li I, and Ca II IRT core emissions, and 2) UVW space velocities finding them to be member candidates to nearby young moving groups and associations. We find a significant percentage of these active/young stars are not members of known aged open clusters, associations, or moving groups. We compare these results to Gaia’s spectral indicator revealing its flaws to detect chromospheric active and young low-mass stars. Ultimately, we share the next steps to study further both young and mature stars in an All-Sky sample, to produce a uniform set of curated stellar properties such as metallicities and ages. These results will comprise a legacy dataset for exoplanet, stellar, and galactic astrophysics.
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